How to calculate calories
Mifflin–St Jeor: BMR = 10W + 6.25H − 5A + s Revised Harris–Benedict: sex-specific weight, height and age coefficients Katch–McArdle: BMR = 370 + 21.6 × lean mass (kg) Maintenance = BMR × activity factor
Worked example. Estimated maintenance energy: 2,375 kcal/day.
Example inputs — Units: US; Sex: Male; Age: 32; Height · feet: 5 ft; Height · inches: 10 in; Weight: 170 lb; Activity level: Light · 1–3 days/week; BMR formula: Mifflin–St Jeor; Energy unit: Calories · kcal. Starting values are illustrative.
Adult educational estimate · not a prescribed intake
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
Estimate resting energy with your selected formula, then multiply by an activity factor. Calories here mean kilocalories; multiply by 4.184 for kilojoules. Deficit amounts illustrate arithmetic, not a personalized diet or guaranteed weight loss.
Using the calories estimate
A calorie estimate is useful for understanding a model of daily energy needs, but it is not a personalized meal prescription. The measurements and activity assumption you enter determine the result. Treat the output as an educational starting point and pay attention to the distinction between estimated maintenance energy and a suggested change for a goal.
Step-by-step inputs
- Units. Replace the starting value with your own, keeping the displayed unit and period. Starting example: US .
- Sex. Replace the starting value with your own, keeping the displayed unit and period. Starting example: Male .
- Age. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 32 .
- Height · feet. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 5 ft.
- Height · inches. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 10 in.
- Weight. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 170 lb.
- Activity level. Replace the starting value with your own, keeping the displayed unit and period. Starting example: Light · 1–3 days/week .
Worked example with the starting values
Using the starting inputs, the estimate is Estimated maintenance energy: 2,375 kcal/day.
Adult educational estimate · not a prescribed intake
- Resting energy · BMR
- 1,727 kcal/day
- 250 kcal deficit illustration
- 2,125 kcal/day
- 500 kcal deficit illustration
- 1,875 kcal/day
Make a useful comparison
Use the measurement units printed beside each field. Check your age, height and weight before interpreting the result, since a unit error can look like an unusually high or low energy need.
Choose activity based on your whole week rather than the hardest session you completed. Work, transport, household movement and rest days all influence actual energy use.
Compare the calorie calculator with the BMR and TDEE tools to understand what is being estimated. Resting energy, total daily expenditure and a goal-based target describe different quantities and should not be used interchangeably.
Common mistakes to avoid
- A calculated target is not a guarantee of a particular weekly weight change. Energy use and intake estimates are uncertain, and short-term weight changes have several causes.
- Do not separately add exercise calories if the activity selection already represents those workouts. Double-counting makes the estimate less useful.
- Standard formulas are not suitable guidance for every person. Children, pregnancy, illness and eating-disorder concerns deserve qualified individual advice rather than a number from a general calculator.
Assumptions & limitations
- Adults only; not appropriate for children, pregnancy, breastfeeding or individualized medical nutrition planning.
- Activity factors and constant calorie deficits are rough estimates, not guarantees of weight change. Consult a clinician or dietitian for personalized targets.
- Katch–McArdle depends on the accuracy of the entered body-fat percentage.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
How do I lose a pound a week?
Eat roughly 500 calories below your maintenance level each day.
Is the result an exact daily requirement?
No. It is an estimate from the entered measurements and activity assumptions, not a measurement of individual metabolism.
Can I use the number as a medical diet plan?
No. It is educational information. A qualified clinician or dietitian can account for medical history and nutritional needs.